Fe Concentrations In Roots Research Articles

Role of EDTA in alleviating lead toxicity in accumulator species of Sedum alfredii H.

The effects of Pb chelater (EDTA–Pb) and ionic Pb (Pb(NO 3) 2) on root cell death, Pb accumulation, changes of ROS, activities of antioxidant enzymes and uptake of mineral elements in response to Pb toxicity in Sedum alfredii H. were compared. Loss of plasma membrane integrity became serious by increasing Pb concentration in the medium, 200 μM Pb + 200 μM EDTA has alleviated the root cell death. The biomass was significantly affected by high concentration of Pb, and root growth was also affected by EDTA–Pb compared with ionic Pb. Lead accumulation was higher in the samples treated with ionic lead than that of the control. The concentration of reactive oxygen species (ROS) was determined by fluorescence microscopy, which indicates that the Pb stress increased the content of ROS significantly, whereas the EDTA–Pb decreased the burst of H 2O 2. High Pb concentrations increase the activity of SOD and LOX. The Cu concentration in root increased significantly under Pb and EDTA–Pb treatment, and 200 μM Pb markedly increased the Fe content in roots. Under ionic Pb condition, the contents of Mg, Ca and K in shoots decreased, whereas they were significantly increased in case of EDTA–Pb. These results suggested that accumulating ecotype of S. alfredii roots were inefficient in uptake of higher concentration of EDTA-chelated Pb for long treatment duration, and that lead toxicity could be alleviated by EDTA.

Effects of Lead, EDTA, and IAA on Nutrient Uptake by Alfalfa Plants

ABSTRACT The element concentrations of alfalfa plants exposed for 10 d to 40 mg lead (Pb) L− 1 from lead nitrate [Pb(NO3)2] alone, or combined with ethylenediaminetetraacetic acid (EDTA) and indole-3-acetic acid (IAA), was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Indole-3-acetic acid at 10 μ M and Pb/EDTA/IAA at 10 μ M increased potassium (K) concentration in roots by 87% and 94%, respectively (P < 0.05). However, IAA at 100 μ M decreased K concentration in leaves (P < 0.05). Plants exposed to 100 μ M IAA, Pb/IAA at 100 μ M, and Pb/EDTA/IAA at 100 μ M had, respectively, 30%, 55%, and 40% more sulfur (S) in leaves than control plants (P < 0.05). Lead and Pb/IAA reduced Ca concentration in stems and leaves (P < 0.05). Conversely, Pb and Pb/EDTA increased Cu concentration in roots and stems. IAA at 100 μ M, Pb, and Pb/EDTA/IAA decreased Zn concentration in roots (P < 0.05). Manganese (Mn) and molybdenum (Mo) concentration in roots and stems was lower in plants treated with Pb and Pb/IAA (P < 0.05). Pb and Pb/IAA reduced (P < 0.05) the iron (Fe) concentration in roots. However, the addition of EDTA and IAA at 10 μ M reduced the negative effects of Pb on Fe absorption.

Al–Fe interactions and growth enhancement in Melastoma malabathricum and Miscanthus sinensis dominating acid sulphate soils

Plants growing in acid sulphate soils are subject to high levels of Al availability, which may have effects on the growth and distribution of these species. Although Fe availability is also high in acid sulphate soils, little is known about the effect of Fe on the growth of native plants in these soils. Two species dominating this soil type in Asia, viz. Melastoma malabathricum and Miscanthus sinensis were grown hydroponically in a nutrient solution with different concentrations of Al and Fe. Melastoma malabathricum is found to be sensitive to Fe (40 and 100 microm). Application of 500 microm Al, however, completely ameliorates Fe toxicity and is associated with a decrease of Fe concentration in shoots and roots. The primary reason for the Al-induced growth enhancement of M. malabathricum is considered to be the Al-induced reduction of toxic Fe accumulation in roots and shoots. Therefore, Al is nearly essential for M. malabathricum when growing in acid sulphate soils. In contrast, application of both Fe and Al does not reduce the growth of M. sinensis, and Al application does not result in lower shoot concentrations of Fe, suggesting that this grass species has developed different mechanisms for adaptation to acid sulphate soils.

Cadmium accumulation in Medicago sativa seedlings treated with salicylic acid

Growth parameters and cadmium accumulation were investigated in alfalfa seedlings treated with 10 &mu;M salicylic acid (SA) at the beginning of seed imbibition. Shoot and root growths were accelerated by SA treatment and suppressed by Cd both in presence and absence of SA. Cd accumulation was stimulated by SA in alfalfa seedlings in dependence of the treatment duration. K, Mg, Ca and Fe contents in roots are decreased in the presence of Cd alone, while SA induces a decrease of Mg, Ca and Fe. Shoot K, Mg and Ca concentrations are increased by Cd only in the absence of SA, while SA induces also an increase of these concentrations, but only in the absence of Cd. High negative correlation of Cd concentration with K and Ca concentrations in root indicates a competition for the same carrier not regulated by SA. Positive correlation between Cd and Mg concentrations in shoots, which is decreased by SA pre-treatment, together with the increase of positive correlation between Cd and Fe concentrations in shoots under the influence of SA, indicates a possible mechanism of SA action through maintenance of ionic homeostasis.

Genotypic Difference in the Responses of Seedling Growth and Cd Toxicity in Rice ( Oryza sativa L.)

The experiment was carried out to study the genotypic difference in the responses of seed germination, growth and physiological characters of rice seedlings to Cd toxicity. The result showed that the germination was slightly stimulated under low Cd concentration (0.01–1.5 mM Cd), while severely depressed under higher Cd concentration (2.0 mM). Rice seedlings exposed to 0.01 mM Cd showed slight increases in plant height, root volume, biomass and chlorophyll concentration. These parameters were significantly reduced when Cd level in the medium was increased to 0.5 mM, and meanwhile corresponding increase in superoxide dismutase (SOD) and peroxidase (POD) activities, and MDA (malondialdehyde) content was observed. However, SOD and POD activities declined when plants were exposed to 1 mM Cd when compared with those under 0.5 mM Cd. Cadmium addition lowered Fe, Cu and Mn concentrations in roots and shoots. There was significant genotypic difference in the response of these parameters to Cd stress. Under Cd stress, Xiushui 110 had the least inhibition of growth and increase in MDA content, higher shoot Cd concentration, and greatest increase in POD and SOD activities, indicating its higher tolerance to Cd toxicity, while Bing 9914 had the greatest reduction of growth, and Zn, Cu, Fe, and Mn contents, but greatest increase in MDA content, and least increase in activities of antioxidative enzymes, indicating its sensitivity to Cd toxicity.

Effects of two iron sources on iron and cadmium allocation in poplar (Populus alba) plants exposed to cadmium

Effects of 10 microM cadmium (supplied as Cd nitrate) on the utilization and allocation of iron (Fe) were investigated in poplar (Populus alba L.) plants grown in nutrient solution with Fe(III)-EDTA or Fe(III)-citrate as the Fe source. The effects of Cd were also compared with those of Fe deprivation. The accumulation of Fe in roots was 10-fold higher in plants grown with Fe-citrate than with Fe-EDTA. Cadmium decreased leaf chlorophyll concentrations and photosynthetic rates, and these decreases were more marked in plants grown with Fe-citrate than with Fe-EDTA. In both Fe treatments, addition of Cd caused large increases in root and shoot apoplasmic and non-apoplasmic Cd contents and increases in root Fe content; however, Cd decreased shoot Fe content, especially in plants grown with Fe-citrate. New leaves of plants grown with Fe-citrate had small cellular (non-apoplasmic) Fe pools, whereas these pools were large in new leaves of plants grown with Fe-EDTA. Non-apoplasmic Cd pools in new leaves were smaller in plants grown with Fe-citrate than with Fe-EDTA, indicating that inactivation of non-apoplasmic Cd pools is facilitated more by Fe-EDTA than by Fe-citrate. In the presence of Cd, Fe-EDTA was also superior to Fe-citrate in maintaining an adequate Fe supply to poplar shoots. Differences in plant responses to Fe-EDTA and Fe-citrate may reflect differences in long-distance transport of Fe rather than in acquisition of Fe by roots.

The Influence of Radiation Quality on the in vitro Rooting and Nutrient Concentrations of Peach Rootstock

The effect of radiation quality (350 - 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.

Amelioration of Manganese Toxicity in Young Rice Seedlings with Potassium

A hydroponic experiment was conducted in a controlled‐temperature glasshouse for 14 days to study the effect of additional potassium (K) on the amelioration of manganese (Mn) toxicity in young rice (Oryza sativa L. cv. Kakehashi) seedlings. Reduced growth, rolling of old leaves, brown spots and interveinal chlorosis on young leaves, and root browning were the main symptoms of Mn toxicity in plants grown with high Mn (1.0 mM) and adequate K (1.0 mM). Application of additional K (10 mM) to the nutrient solution increased chlorophyll concentration and dry matter yields of plants grown in high Mn, but did not restore dry matter accumulation to the level achieved in the control plants. Plants grown in 1.0 mM Mn and 10 mM K had lower tissue Mn concentration on a dry matter basis than plants grown in 1.0 mM Mn and 1.0 mM K and did not show leaf injury symptoms, but still showed root browning; however, the accumulation (per plant basis) of Mn was approximately the same, indicating that additional K increased the tolerance of the plant to high Mn. The concentration and accumulation of iron (Fe) in shoots of plants grown at 1.0 mM K with 1.0 mM Mn was lower than in the control plants, indicating an inhibition of Fe translocation to shoots by high Mn. Additional K increased both concentration and accumulation of Fe in shoots and roots of plants grown in high Mn. The higher phosphorus (P), K, zinc (Zn), and copper (Cu) concentrations in shoots and roots of plants grown in 1.0 mM Mn and 1.0 mM K could be a concentration effect because of severe growth reduction, while lower calcium (Ca) and magnesium (Mg) concentrations were probably due to competition with Mn at the absorption sites. Additional K further decreased Ca and Mg concentrations, indicating possible interference of K with the absorption and physiological availability of Ca and Mg. Additional K increased K concentrations and decreased P, Cu, and Zn concentrations in shoots and roots of plants grown with high Mn. These results suggest that additional K can partially alleviate the symptoms of Mn toxicity and Mn‐induced Fe deficiency in rice seedlings and significantly improve plant growth.

Metal physiology and accumulation in a Medicago truncatula mutant exhibiting an elevated requirement for zinc

Summary • A novel, metal accumulating mutant of Medicago truncatula was characterized for tissue metal concentrations, plant growth, percent leaf loss, and leaf-cell metal influx capacity relative to wild-type plants. • Growth, mineral parameters, and functional analyses were determined using plants grown hydroponically in complete nutrient solutions with varying levels of Zn and Mn. • Depending on the growth regime, the mutant exhibited leaf necrosis, and was found to have elevated concentrations of Zn, Mn, and Cu in most tissues, along with elevated Fe concentrations in roots. General growth was reduced, and percent leaf loss was elevated relative to nutritionally replete wild-type plants, but was similar to Zn-deficient wild-type plants. Growth of the mutant on moderately elevated Zn levels, in combination with lowered Mn, reduced leaf necrosis in new leaves. • We have named the mutant and its recessive mutation raz, for requires additional zinc, because leaf necrosis is reduced when plants contain elevated Zn levels. Due to its similarities to Zn-deficient wild-type plants, the raz mutant should serve as a useful model to study micronutrient metal homeostasis.

Apoplastic accumulation of iron in the epidermis of maize (Zea mays) roots grown in calcareous soil

High concentrations of Fe in the roots of plants grown in calcareous soil have been found in a variety of plants, which, nevertheless, show Fe deficiency symptoms. In the present work, energy dispersive X‐ray (EDX) analysis at the cellular level has been used to characterize high root Fe concentrations in maize (Zea mays L.) grown in a calcareous soil in comparison with low root Fe concentrations under acidic soil conditions. Roots were thoroughly washed to remove adhering soil particles from the root surface as far as possible. To avoid any interference with possibly still present soil particles, the excitation beam was focused on radial walls of neighboring cells as well as on the symplast. Under alkaline conditions, high Fe concentrations in the mM range and higher accumulated in the epidermal root apoplast. Symplastic Fe was not detectable. Only traces of Fe were detectable in the apoplast of the cortex parenchyma. Under acidic conditions, apoplastic root Fe concentrations were clearly lower than under alkaline conditions, and no Fe was detectable in the root apoplast by use of EDX analysis. We conclude that, under alkaline conditions, high amounts of Fe are trapped in the epidermal root apoplast (apoplastic Fe inactivation), probably because of a high apoplastic pH and thus restricted translocation towards the root stele and to the upper plant parts. In contrast, on acidic soils Fe translocation towards the root stele and thus Fe supply to the upper plant parts was not impaired. Our findings imply that Fe deficiency on calcareous soils is not caused by restricted acquisition of Fe from the soil.

Impact of nitrogen form on iron uptake and distribution in maize seedlings in solution culture

Comparative studies on the effect of nitrogen (N) form on iron (Fe) uptake and distribution in maize (Zea mays L. cv Yellow 417) were carried out through three related experiments with different pretreatments. Experiment 1: plants were precultured in nutrient solution with 1.0×10−4 M FeEDTA for 6 d and then exposed to NO3–N or NH4–N solution with 1.0×10−4 M FeEDTA or without for 7 d. Experiment 2: plants were precultured with 59FeEDTA for 6 d and were then transferred to the solution with different N forms, and 0 and 1.0×10−4 M FeEDTA for 8 d. Experiment 3: half of roots were supplied with 59FeEDTA for 5 d and then cut off, with further culturing in treatment concentrations for 7 d. In comparison to the NH4-fed plants, young leaves of the NO3-fed plants showed severe chlorosis under Fe deficiency. Nitrate supply caused Fe accumulation in roots, while NH4–N supply resulted in a higher Fe concentration in young leaves and a lower Fe concentration in roots. HCl-extractable (active) Fe was a good indicator reflecting Fe nutrition status in maize plants. Compared with NO3-fed plants, a higher proportion of 59Fe was observed in young leaves of the Fe-deficient plants fed with NH4–N. Ammonium supply greatly improved 59Fe retranslocation from primary leaves and stem to young leaves. Under Fe deficiency, about 25% of Fe in primary leaves of the NH4-fed plants was mobilized and retranslocated to young leaves. Exogenous Fe supply decreased the efficiency of such 59Fe retranslocation. The results suggest that Fe can be remobilized from old to young tissues in maize plants but the remobilization depends on the form of N supply as well as supply of exogenous Fe.

Significance of root exudates in acquisition of heavy metals from a contaminated calcareous soil by graminaceous species

Graminaceous species release phytosiderophores for mobilization of iron (Fe) under Fe deficiency stress. In this study the possible risk that these root exudates might also enhance the uptake of toxic heavy metals from contaminated soils, was investigated. For this purpose wheat (Triticum aestivum L. cv. Piko) and sorghum (Sorghum bicolor (L.) Moench cv. E‐610), differing in release of phytosiderophores were precultured with roots in nylon bags in a sand culture system for low and high Fe nutritional status (+/‐Fe supply) for two weeks. After this preculture the nylon bags were brought in contact with a sewage sludge or heavy metal salt‐contaminated calcareous soil in a climate chamber for an additional 8 days growth period. At harvest the concentration of Fe, Zn, Ni and Cd in roots and shoots were analysed. The results clearly show that both plant species have mobilized Fe and heavy metals from the contaminated soil. Plants precultured for low Fe nutritional status had a higher uptake of Fe, Zn, Ni and Cd (up to 200%) than control plants with adequate Fe nutritional status. This enhanced acquisition of heavy metals was particularly expressed in wheat as an Fe efficient graminaceous species with corresponding higher release of phytosiderophores under Fe deficiency stress than sorghum.

The central role of microbial activity for iron acquisition in maize and sunflower

Maize (Zea mays L.) and sunflower (Helianthus annuus L.) grown on a calcareous soil showed poor growth and/or were chlorotic in spite of abundant Fe in the roots. It has been hypothesized that microbial siderophores chelate Fe (III) in the soil, and that in this form Fe is transported towards the root apoplast. On the calcareous soil, total and apoplastic root Fe concentrations were high, probably because of a high apoplastic pH depressing Fe (III)-reductase activity and thus the Fe2+ supply to the cytoplasm. On the acidic soil, total and apoplastic root Fe concentrations were low, probably because of a low apoplastic pH favouring Fe (III) reduction, hence plants showed no Fe-deficiency symptoms. The main objective of the present work was to investigate the role of microbial soil activity in plant Fe acquisition. For this purpose, plants were grown under sterile and non-sterile conditions on a loess loam soil. Plants cultivated under non-sterile conditions grew well, showed no Fe-deficiency symptoms and had fairly high Fe concentrations in the roots in contrast to plants grown in the sterile medium. Low root and leaf Fe concentrations in the axenic treatments indicated that the production of microbial siderophores was totally suppressed. Accordingly, sunflowers were severely chlorotic and this was associated with very poor growth, whereas in maize only growth was drastically reduced. In maize under sterile conditions, root apoplastic and total Fe concentrations were not as low as in sunflowers, which may have indicated that phytosiderophores produced in maize partly sustained Fe acquisition, but due to poor growth were not as efficient in supplying Fe as microbial activity under natural conditions. It may be therefore assumed that in natural habitats soil microbial activity is of pivotal importance for plant Fe acquisition.

Foliar application of iron as a remedy for zinc toxic tomato plants

Two tomato [Lycopersicon esculentum) cvs. Blizzard and Liberto, were grown hydroponically in a Controlled Temperature (CT) room for five weeks to investigate the effectiveness of foliar application of supplementary iron (Fe) to the leaves of plant grown at high zinc concentration (5 mg L−1). Zinc (Zn) concentrations were 0.5 or 5 mg L−1 in complete nutrient solution. One week after application of Zn at 5 mg L−1, supplementary iron ( 28 mg L−1 for a week and 56 mg L−1 for a week) was supplied via leaves to the plants grown at 5mg L−1 Zn. The plants grown at 5mg L−1 Zn produced less dry matter and chlorophyll than those at 0.5mg L−1 for both cultivars. Foliar application of supplementary iron resulted in increases in dry matter and chlorophyll concentrations for both cultivars. These increases were greater in Liberto than in Blizzard. Zinc concentration in plant tissues increased to toxic levels for both cultivars in the high zinc treatment. Application of supplementary Fe as a foliar spray decreased Zn concentration in the leaves and roots of plants grown at high Zn, but its concentrations were still at detrimental levels. Iron concentration in leaves declined to the deficient level in the high (5 mg L−1) Zn treatment, but was markedly increased in the roots. Application of supplementary Fe corrected Fe deficiency in leaves of plants grown at 5mg L−1 Zn and reduced root Fe concentrations.

Overestimation of apoplastic Fe in roots of soil grown plants

The concentration of apoplastic Fe in roots of soil-grown plants was determined in order to evaluate the possible significance of the root apoplast as storage pool for Fe. Roots were grown in membrane bags maintaining contact with the soil solution but without direct contact with the soil. It could be shown that the concentration of apoplastic Fe in roots grown in most soils was lower than 50 mg kg-1 root dry matter. This concentration is much lower than previously reported from nutrient solution and soil-grown cultures (about 1000 mg kg-1 dry matter). The concentration of apoplastic Fe in strategy I and strategy II plants was little affected by the different soils used. Direct contact of roots with soil led to soil contamination at the root surface and so to an overestimation of the apoplastic Fe pool. Soil contamination of roots grown in direct contact with soil was detected by measuring the soil markers Ti, Si and Al and was further shown by PIXE. In conclusion, the low concentration of apoplastic Fe in roots demonstrates that the root apoplast is less significant as storage pool for Fe than previously assumed.

MICRO-PIXE EVALUATION OF Fe DISTRIBUTION IN BARLEY ROOTS

High Fe concentrations were reported from roots of plants grown in soil. This has been discussed as a possible Fe source for plants, since the concentrations shown in the roots were much higher than in the shoots. There are, however, also some indications that soil contamination at the root surface of soil grown plants could have led to an overestimation of the Fe concentration in roots. Fe distribution in root cross sections of barley (Hordeum vulgare L. cv. Alexis) has been studied to investigate this hypothesis. Micro-PIXE analyses in point and mapping mode were complemented by the STIM technique. Based on the correlation between Fe and soil-related elements ( Ti , Al and Si ), most of Fe located at the root surface could be attributed to soil contamination. It could also be shown that this soil contamination leads to an overestimation of Fe concentration in roots.

Physiological and biochemical changes in young maize plants under iron deficiency. 3. Concentration and distribution of some nutrient elements

Young maize plants (hybrid Knezha‐650), grown hydroponically, were supplied with different amounts (7.5–0 mg Fe L‐1) of iron (Fe). At 14, 21, and 28 days, concentrations of Fe, phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn), and copper (Cu) in leaves were determined. Iron deficiency resulted in rapid and strong decrease of root Fe concentration. Despite the low total Fe in the leaves of chlorotic plants, the Fe concentration in leaves did not reflect the Fe supply to plants. In Fe‐deficient plants, the tissue concentrations of nutrient elements other than Fe changed too, the alterations in the studied microelements being greater. Changes in Mn and Zn concentrations in leaves depended highly on the degree of Fe deficiency. Copper transport to leaves seemed to be hampered and the main part of it was retained by roots. As compared to control plants, the portion of Fe, Mn, and Ca in roots was smaller in chlorotic plants. The opposite trend was found for Cu and Mg. Increased Zn/Fe, Mn/Fe, and possibly P/Fe ratios might be related to Fe inactivation in leaves under Fe deficiency. Plants supplied with 1/10 of optimum Fe required “adapted”; partially to Fe deficiency which was expressed by a smaller departure from the norm for micronutrient concentrations in leaves at the end of the experiment as compared to the earlier stages of growth.

The effect of nitrate nutrition on iron chlorosis and leaf growth in sunflower ( Helianthus annuus L.)

The objective of this work was to investigate the effects of nutrient solution pH, nitrogen form (NO 3, NH 4NO 3), bicarbonate and different Fe concentrations in the nutrient solution on the Fe concentration in roots and on the development of Fe deficiency symptoms in sunflower plants ( Helianthus annuus L.). High pH in the nutrient solution induced by nitrate supply or by a pH-stat device led to increased Fe concentrations in roots and low leaf Fe concentrations associated with a significant decrease in leaf chlorophyll concentration manifested by yellow leaves. Plants of the nitrate fed treatments with 1 μM Fe in the nutrient solution were also characterized by reduced leaf growth and by the suppression of new leaf formation. The reduced leaf growth and the suppression of new leaves only occurred with nitrate and not with NH 4NO 3 in all treatments with 1 μM Fe in the nutrient solution. All symptoms were removed by a high Fe concentration in the nutrient solution (100 μM) at low external pH proving that suppression of leaf formation, reduced leaf growth and low chlorophyll concentration were caused by Fe deficiency. In the nitrate treatment with a low Fe supply (1 μM Fe) and pH 4 in the nutrient solution leaf chlorophyll concentrations similar to the controls were found. In comparison to control plants (NH 4NO 3, 1 μM Fe), leaf growth was still significantly reduced, and new leaf formation was suppressed. The chlorophyll concentration and CO 2 assimilation rate did not differ from those of the control plants. These results show that Fe deficiency is also characterized by small green leaves and the suppression of leaf formation. At the onset of leaf development, leaf growth and new leaf formation may respond more sensitively to poor Fe efficiency than chlorophyll concentration. In experiments with NO 3 plus HCO 3, simulating soil solution conditions prevailing in calcareous soils, the Fe efficiency of the youngest leaves was poor, showing retarded leaf growth and low chlorophyll concentration.

The influence of pH on root morphology and mineral content of Pinus pinaster Ait. seedlings

ABSTRACT Two-week old seedlings of Pinus pinaster Ait. were grown in nutrient solutions at pH values ranging from 3.5 to 6.5. Acidity exerted a different influence on the growth of the main and lateral roots, thus changing the morphology of the whole root system. Roots grown at pH 3.5 had the shortest length, but the highest biomass and were markedly thickened. The total number of 2nd order lateral roots per plant was not significantly influenced by pH, whereas their length and the development of 3rd order roots were the highest at pH 3.5 and the lowest at pH 6.5. Mineral nutrition was affected by the pH of the culture solution. The P and Fe concentrations in roots were higher in the pH 3.5 and 4.5 solutions than in pH 5.5 and 6.5. In contrast, lower K, Ca, Mg and especially Mn contents were found in the roots grown at pH 3.5. However, needle dry weight was unaffected by low pH and neither chlorosis nor critical levels of mineral elements were observed. These results suggest that the compensatory growth of lateral roots allows P. pinaster seedlings to maintain an adequate nutritional status in the shoot even under highly acidic conditions.

Influence of phosphorus on the growth and ergot alkaloid content of Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E−) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E− plants. Endophyte infection increased specific root length at 17 and 50 mg P kg-1soil. At soil P level of 17 mg P kg-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E− plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg-1 but declined again at 96 mg P kg-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue.